PDF file of all lecture notes for the Processes in Ecology and Evolution course (code BioSciE106) at the University of California, Irvine. Notes are organized and labeled by their corresponding textbook chapter in Ecology: Evolution, Application, Integration (2nd Edition) by David T. Krohne.
Cont...
Course: Processes in Ecology and Evolution
Course Code: BioSciE106
LESSON 1: Ch.1 - Introduction to Ecology
Learning objectives: (1) define ecology...
● ➣Ecology: the study of interactions b/w organisms and its biological/physical
environment.
● Change in fur color over the seasons exemplifies ecology.
○ ➣Ex. Hares respond to weather/climate as well as habitat and vegetation, to
camouflage themselves in response to competitors/predators.
● Ecological research proceeds by asking specific research questions. Questions can
address proximate/ultimate factors.
○ Proximate factors: the direct mechanisms responsible for an observation.
○ Ultimate factors: the reason why or the evolutionary basis for an observation (i.e.
effect on fitness, predator success, genetic changes).
● ➣Levels of biological organization:
● 1. Organismal: focuses on the interactions b/w individuals and their environment.
● 2. Population: interactions b/w groups of individuals of a given species and their
environment.
● 3. Community: interactions b/w different yet coexisting species, mediated by the shared
environment.
● 4. Ecosystem: all interacting living (biotic) and nonliving (abiotic) components of a
community.
● 5. Biosphere: all ecosystems on Earth.
● Fundamental themes
● A. Adaptations: a trait or combination of characteristics that INC an individual’s fitness.
● B. Evolutionary fitness: probability of surviving/reproducing-- dependent on
environmental context.
● C.Selection pressure: the environmental factors (biotic or abiotic) that determine fitness.
● D. Evolution-ecology connection: pervasive and continuous, aka still changing due to
selection pressure.
○ Encompasses the organism, physical environment, and the systems of
interactions.
● E. There is no “inherent balance of nature.”
○ Equilibrium and non-equilibrium in ecological processes are important in modern
ecology.
● F. The human impact is pervasive and extreme.
● Ecology is a quantitative science: observations lead to testable predictions; ecologists
often use “model biological systems” as basic biology and natural history are well-known;
ecologists can also use other study systems for when it is appropriate for their question;
complex mathematics/stats are required to understand these complex systems.
,Course: Processes in Ecology and Evolution
Course Code: BioSciE106
LESSON 2: Ch.2 - Adaptation and Evolution
Learning Objectives: (1) explain how the theory of natural selection (NS) was developed, (2)
define evolution and be able to distinguish evolutionary biology research from others, (3)
describe the mechanisms of evolution and be able to predict which mechanism(s) have the
most impact under different scenarios, (4) define the term adaptation.
● I. Developing the Theory of Evolution by NS
● A. Voyage of HMS Beagle, 1831-36.
○ 1. Darwin was the ship’s naturalist; the objective was to improve colonialist maps
particularly of South America.
● B. Scale of Geological Time
○ 1. Uniformitarianism: modern land forms arose slowly by gradual processes.
● C. Trait Variation
○ 1. Darwin observed traits that varied and diversified w/ geography.
● D. Local Arguments
○ 1. Heritable variation within species.
○ 2. Organisms can have high reproductive potential.
○ 3. Intense competition limits reproduction and survival.
● Conclusion: evolution by natural selection.
○ Individuals with inherited traits that INC their fitness will INC in frequency in the
population.
○ A potential mechanism by which evolution can occur.
● Darwin’s limitations
○ 1. Mechanism of inheritance was not understood,
○ 2. Concept of the gene was unknown,
○ 3. Darwin’s ideas were correct (and have been supported by subsequent science
repeatedly) but INCOMPLETE-- other mechanisms of evolution also exist.
● II. What is evolution?
● Genetic change in a population over time.
○ Focus on population gene pool (sum total of all alleles in the population).
● Phenotype: genotype + environmental factors.
● Changes in the gene pool can be modeled using Hardy-Weinberg equilibrium.
○ 1. Represents no evolution, or no change in allele frequencies.
○ 2. What mechanisms can cause a population to deviate from HW equilibrium.
● III. Mechanisms of evolution
● HW equilibrium rests in 4 assumptions; if violated, EVOLUTION occurs.
Assumption Mechanism of evolution occurring if
violated
No differential success of genotypes. *Natural selection
Population is infinitely large w/ random *Genetic drift
mating.
No net immigration or emigration by *Gene flow
genotype.
,Course: Processes in Ecology and Evolution
Course Code: BioSciE106
No new mutations (mutations are Mutation pressure
important for generating new alleles, but
they are so rare the effects of selection,
drift, and gene flow are much larger).
○ Ranked from most impactful* to least on shaping Goby population genotypes.
● Mechanism1: Selection
○ A. Based on Darwin’s Theory of Selection.
○ B. Differential survival/reproduction is key quantified w/ the selection coefficient s
(proportion of a genotype that is not represented in the next generation). s=1 ->
100% of the genotype is absent in the next generation.
○ C. Types of selection:
■ Directional selection: one extreme phenotype is favored.
■ Stabilizing selection: intermediate phenotype is favored.
■ Disruptive selection: when both extreme phenotypes are favored.
● Mechanism2: Genetic drift
○ A. Random changes in allele frequencies.
○ B. More pronounced in smaller populations.
, Course: Processes in Ecology and Evolution
Course Code: BioSciE106
○ C. Non-Darwinism evolution. (Darwin did not consider during his time-- isn’t that
all remaining mechanisms as well?)
● Mechanism3: Gene flow
○ A. Net movement of an allele to / from a population, results in changes in allele
frequencies.
○ B. Can reinforce or oppose changes that occur by selection and drift.
○ C. Isolated populations will be more affected by natural selection (and genetic
drift in particular if population is small).
● IV. How do adaptations arise?
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